crypter.cpp

// Copyright (c) 2009-2021 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <wallet/crypter.h>

#include <crypto/aes.h>
#include <crypto/sha512.h>
#include <util/system.h>

#include <vector>

namespace wallet {
int CCrypter::BytesToKeySHA512AES(const std::vector<unsigned char>& chSalt, const SecureString& strKeyData, int count, unsigned char *key,unsigned char *iv) const
{
    // This mimics the behavior of openssl's EVP_BytesToKey with an aes256cbc
    // cipher and sha512 message digest. Because sha512's output size (64b) is
    // greater than the aes256 block size (16b) + aes256 key size (32b),
    // there's no need to process more than once (D_0).

    if(!count || !key || !iv)
        return 0;

    unsigned char buf[CSHA512::OUTPUT_SIZE];
    CSHA512 di;

    di.Write((const unsigned char*)strKeyData.data(), strKeyData.size());
    di.Write(chSalt.data(), chSalt.size());
    di.Finalize(buf);

    for(int i = 0; i != count - 1; i++)
        di.Reset().Write(buf, sizeof(buf)).Finalize(buf);

    memcpy(key, buf, WALLET_CRYPTO_KEY_SIZE);
    memcpy(iv, buf + WALLET_CRYPTO_KEY_SIZE, WALLET_CRYPTO_IV_SIZE);
    memory_cleanse(buf, sizeof(buf));
    return WALLET_CRYPTO_KEY_SIZE;
}

bool CCrypter::SetKeyFromPassphrase(const SecureString& strKeyData, const std::vector<unsigned char>& chSalt, const unsigned int nRounds, const unsigned int nDerivationMethod)
{
    if (nRounds < 1 || chSalt.size() != WALLET_CRYPTO_SALT_SIZE)
        return false;

    int i = 0;
    if (nDerivationMethod == 0)
        i = BytesToKeySHA512AES(chSalt, strKeyData, nRounds, vchKey.data(), vchIV.data());

    if (i != (int)WALLET_CRYPTO_KEY_SIZE)
    {
        memory_cleanse(vchKey.data(), vchKey.size());
        memory_cleanse(vchIV.data(), vchIV.size());
        return false;
    }

    fKeySet = true;
    return true;
}

bool CCrypter::SetKey(const CKeyingMaterial& chNewKey, const std::vector<unsigned char>& chNewIV)
{
    if (chNewKey.size() != WALLET_CRYPTO_KEY_SIZE || chNewIV.size() != WALLET_CRYPTO_IV_SIZE)
        return false;

    memcpy(vchKey.data(), chNewKey.data(), chNewKey.size());
    memcpy(vchIV.data(), chNewIV.data(), chNewIV.size());

    fKeySet = true;
    return true;
}

bool CCrypter::Encrypt(const CKeyingMaterial& vchPlaintext, std::vector<unsigned char> &vchCiphertext) const
{
    if (!fKeySet)
        return false;

    // max ciphertext len for a n bytes of plaintext is
    // n + AES_BLOCKSIZE bytes
    vchCiphertext.resize(vchPlaintext.size() + AES_BLOCKSIZE);

    AES256CBCEncrypt enc(vchKey.data(), vchIV.data(), true);
    size_t nLen = enc.Encrypt(vchPlaintext.data(), vchPlaintext.size(), vchCiphertext.data());
    if(nLen < vchPlaintext.size())
        return false;
    vchCiphertext.resize(nLen);

    return true;
}

bool CCrypter::Decrypt(const std::vector<unsigned char>& vchCiphertext, CKeyingMaterial& vchPlaintext) const
{
    if (!fKeySet)
        return false;

    // plaintext will always be equal to or lesser than length of ciphertext
    int nLen = vchCiphertext.size();

    vchPlaintext.resize(nLen);

    AES256CBCDecrypt dec(vchKey.data(), vchIV.data(), true);
    nLen = dec.Decrypt(vchCiphertext.data(), vchCiphertext.size(), vchPlaintext.data());
    if(nLen == 0)
        return false;
    vchPlaintext.resize(nLen);
    return true;
}

bool EncryptSecret(const CKeyingMaterial& vMasterKey, const CKeyingMaterial &vchPlaintext, const uint256& nIV, std::vector<unsigned char> &vchCiphertext)
{
    CCrypter cKeyCrypter;
    std::vector<unsigned char> chIV(WALLET_CRYPTO_IV_SIZE);
    memcpy(chIV.data(), &nIV, WALLET_CRYPTO_IV_SIZE);
    if(!cKeyCrypter.SetKey(vMasterKey, chIV))
        return false;
    return cKeyCrypter.Encrypt(*((const CKeyingMaterial*)&vchPlaintext), vchCiphertext);
}

bool DecryptSecret(const CKeyingMaterial& vMasterKey, const std::vector<unsigned char>& vchCiphertext, const uint256& nIV, CKeyingMaterial& vchPlaintext)
{
    CCrypter cKeyCrypter;
    std::vector<unsigned char> chIV(WALLET_CRYPTO_IV_SIZE);
    memcpy(chIV.data(), &nIV, WALLET_CRYPTO_IV_SIZE);
    if(!cKeyCrypter.SetKey(vMasterKey, chIV))
        return false;
    return cKeyCrypter.Decrypt(vchCiphertext, vchPlaintext);
}

bool DecryptKey(const CKeyingMaterial& vMasterKey, const std::vector<unsigned char>& vchCryptedSecret, const CPubKey& vchPubKey, CKey& key)
{
    CKeyingMaterial vchSecret;
    if(!DecryptSecret(vMasterKey, vchCryptedSecret, vchPubKey.GetHash(), vchSecret))
        return false;

    if (vchSecret.size() != 32)
        return false;

    key.Set(vchSecret.begin(), vchSecret.end(), vchPubKey.IsCompressed());
    return key.VerifyPubKey(vchPubKey);
}
} // namespace wallet